Fig. 4. Fore-paw of kitten embryo, ca. 90 mm. Volar surface. 
Fig. 5. Fore-paw of kitten embryo, 35 mm. Volar surface. 
Fig, 6. Same as above, profile, and drawn to a somewhat larger scale. 
Fig. 7. Fore-paw of rat embryo, 20 mm. Volar surface. 
tres of disturbance in the epidermic ridges of the 
arboreal Primates seem to render it certain that the 
latter structures are the rudiments of the former. I 
have made a few other comparisons, and find in all cases a similar 
arrangement of pads, which may be readily named after the termino- 
logy adopted for Inuus. Thus in the rat (Fig. 7, embryo) the thenar 
pad is distinct from the apical pad of the thumb. The projection on 
the ulnar side, lower down on the wrist, seems to correspond to the 
little mound on the cat’s paw which bears the tuft of bristles rather 
than to the large hypothenar spur. This latter is seen above and in 
line with the thenar pad. 
Comparison with the foot. A brief general comparison of 
the soles of the hind feet of various mammals, considering the epi- 
dermic whorls the equivalent of pads, has yielded the following result. 
The arrangement and number of the pads is much the same as upon 
the fore feet, the apical, thenar and the three palmar being quite 
constant. The hypothenar often fails, especially among the Primates, 
and there is often a second thenar pad upon the hallucal side and 
behind the true thenar. The necessity for this seems to be the in- 
crease in the length of the sole due to the prolonged os calcis. It 
appears especially well developed in the rat, and its place was indi- 
cated in one of the Cebi by an epidermic whorl. The cat shows no 
hypothenar and both the thenar and the first apical are gone with 
the complete reduction of the thumb. On the hind foot of Inuus 
tiie palmar and thenar centres were well marked. The hypothenar 
